Cellphones are taking over the world
In the swiftly advancing world that is today's technology market, gadgets of all sorts, shapes and sizes appear with a voracity that few can keep up with.
The monolithic ideals that consumers shared for electronics, not 20 years ago, are now unduly passé, and resemble nothing but notions of a prehistoric, or in this case, a pre- digital era.
The world today is all about a wireless, handheld, mobile, battery-powered and operated, computer-driven, seamlessly integrated and converged network of electronics. It is the nature of digital technology to evolve into less power-hungry, lighter, smaller, better, faster, cooler and more useful items for mass consumption.
These gadgets are intended to make our lives more simple and easy while providing us consumers with a less of a hassle and burden in the process.
One gadget that has been both the victim of a lot of criticism and regulation, in addition to becoming one of the fastest growing and spreading technologies within the last decade has been the cell phone.
Even though studies show that 50% of Americans these days have cell phones, in comparison to other markets, the technology is still catching on here. Cell phones are more popular in other countries -- 90% of both the European and Asian populations own cell phones.
And though cell phones have gotten lighter, consume less battery power, and have begun to incorporate pictures, video, email, web browsing and personal digital assistant (PDA) like organizational features, understanding how the base technology works is still not common knowledge among the population.
There is a reason millions of people in the United States and around the world use cellular phones, they are one gadget that has undoubtedly changed the way we think, conduct business and effected our ability of productiveness, all for the better.
Possessing the ability to talk to anyone on the planet from just about anywhere makes these devices very useful in a number a facets, whether it's calling 911 after an accident or simply phoning home to see what's for dinner, the portable phone is a device few other electronics can touch in terms of impact on consumers.
These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace.
The newest and hottest phones now come with the ability to store contact information; make tasks and to-do lists; keep track of appointments and set reminders; set and download ring tones for certain numbers; send and receive email, pictures and video files; get information (news, entertainment, stock quotes) from the internet; play video games, as well as become complete PDA's, MP3 players and global positioning satellite (GPS) receivers.
"In essence, a cell phone is a radio," said Brian Katcher, wireless expert at Barbeck Communications Group. "The cell phone is an extremely sophisticated radio, but a radio nonetheless," he continued.
The telephone itself was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in 1880, by the nature of each technology, it was near inevitable the two technologies would eventually merge.
Before cell phones, people who really needed mobile-communications installed radio telephones in their cars. This was a system that had one central antenna tower -- allowing for approximately 25 radio channels -- per city.
This central antenna meant that any car using it needed a powerful enough transmitter to transmit a signal 40 to 50 miles at any one time, and even though people could use these as telephone, there weren't enough channels to make this technology a viable option for communication.
What cell technology allowed us to do was divide cities into smaller "cells," so that certain frequencies could be reused across any particular city, Katcher said.
By reusing certain frequencies across a certain area, more people have access to use of a cell phone.
"In a typical analog cell-phone system in the United States, a cell phone carrier receives about 800 radio frequencies to use across a city," Khurram Khan said, sales manager at T-Mobile.
A carrier will then chop a city into cells -- typically a hexagonal estimated area of 10 square miles -- by using special antennas, or base stations/towers. Since both cell phones and base stations use low-power transmitters, the same frequencies can be used in non-adjacent cells without fear of the signal crossing over with another one.
"When companies refer to the amount of their 'coverage,' they are referring to the area in which they have covered by their own antennas," said Carol Peterson, sales consultant for U.S. Cellular. Fulfilled
Each cell in an analog system uses only a portion of the available channels it has.
"If you take a grid of seven cells in a city, each cell will use only one seventh of its available channels to further insure that there are no signal collisions," Katcher said.
A cell phone uses two frequencies per call, one frequency for sending and signal and one frequency for receiving a signal, this is call a "full duplex channel," Katcher said.
In 1983, the analog cell phone standard, called Advanced Mobile Phone System (AMPS), was approved by the FCC, and was planned to use a range of frequencies between 824 megahertz (MHz) and 894 MHz.
In order to insure and encourage competition in this fledgling market, the U.S. government required the presence of two carriers in every market, or city; known as carriers A and B.
Each carrier was assigned 832 frequencies: 790 for voice and 42 for data. The transmit and receive frequencies of each voice channel are separated by 45 MHz to keep them from interfering with one another.
The frequencies used in these analog voice channels were set to be 30 kilohertz kHz -- a size that would give the cell phone comparable voice quality to that of a land phone line.
Because cell phone carriers only have 832 radio frequencies for an analog signal, they must maximize the number of signals each cell phone can have. Since all cell phones are full duplex, and use two radio frequencies (or one channel) per call, there are 416 channels available per carrier.
21 of these channels are used as service channels, thus allowing calls on the remaining 395 voice channels.
With 395 voice channels available for every cell grid of seven cells, any one analog cell phone has about 56 voice channels available for making calls around a city. This allows for 56 people to be talking on their cell phones at any one time.
Since cell phone signals do not make it very far outside the 10 square mile range, or the size of one cell, these same frequencies can be reused throughout the entirety of a cell grid, said Katcher.
"What makes the portability of cell phones possible is the low power consumption of these small transmitters," Arron Holland said, store manager at Nextel. Lower power means smaller batteries, smaller batteries means smaller phones he finished.
The drawback to the "cellular" approach is that it requires a massive amount of antennas to cover an area, Khan said. "A typical city will usually have hundreds of cell phone towers, the only way the cost remains low is because of the number of users each company has."
In addition to operating a large amount of cell phone towers, each cell phone carrier rims a central office called a Mobile Telephone Switch Office (MTSO). The job of this office is to handle all phone connections to normal land-based phone systems as well as control the channels being used by each antenna.
There is a specific method and order to how a call will get from one place to another; a large portion of this has to do with cell phone codes, these phones are often used to identify the phone, the phone's owner and the service provider.
Once a person powers on their phone, the phone begins to automatically listen or search for a System Identification code (SID - a special service number assigned to each phone provider that will identify their service) on a service channel.
The service channel is a special frequency that the phone and cell towers use to talk to each other. These channels are used for setting up calls, changing cell channels, ending service and the like. A phone will display an "out of range" or "no service message if it cannot find a service channel in which to connect to.
Once the phone receive a SID, the phone then compares it to the SID programmed into the phone, if the numbers match, then the phone knows it's communicating with it's own system. If the SID on the service channel does not match the SID programmed into the phone, then the phone displays a "roaming" message.
After a phone verifies an SID number, the phone will transmit a registration request to the MTSO, this keeps the MTSO informed as to which cell a person is in when it wants to send a call to a phone.
Once the MTSO receives a call for that phone, it chooses a channel in which to transmit the call in the cell you're currently in.
The MTSO contacts the cell tower a person is using to connect, to discover which frequencies are in use; once the MTSO sends the signal for your phone and the tower to switch to the available frequencies, a call is connected. It is at this point that you are talking -- technically -- by a two way radio to a person on the other end of the line.
If a person is traveling during a call, the cell tower a person is currently connected to will note that the signal strength is diminishing and the cell tower a person is moving towards will note that the signal strength is increasing.
These two towers will then coordinate with each other through the MTSO, and at some point, a phone will receive a message to switch frequencies, handing the call off to the tower a person is now closest to.
As people travel signals are passed from cell to cell, Katcher said. And when a phone say's 'signal lost,' or 'faded' is generally because one of the towers lost track of the position of your cell phone or a person got too far away from a tower for it to continue the transmission, he finished.
Digital cell phones use the same radio technology as analog phones, but they use it in a different way. Analog systems are notorious for using their bandwidths inefficiently, which is also why they can only offer a fraction of the available channels that a fully digital network can.
"Digital networks can fit more channels within a given bandwidth," said Ed Kelly, sales assistant at Cingular.
Digital phones convert your voice into binary information (1's and 0's that computers read as data) and then compresses it. This compression allows for up to 10 digital calls to occupy the space of a single analog call, said Katcher.
To encode, send, receive and decode digitally compressed signals, cell phones need to contain a large amount of processing power. So in addition to the liquid crystal display (LCD), antenna, keyboard, microphone, speaker and battery, cell phones need to use a fairly complex -- and small -- circuit board.
The circuit board of a cell phone is the heart and the brain of the system said Holland. Cell phone circuit boards today contain a lot more things now then they did when they were first released.
They now have digital signal processors and analog to digital processors to encode and decode sound, microprocessors for advanced computer-like tasks and they contain ROM's and flash memory to hold the operating system and date book, phone book, picture and sound information. The displays have grown in size, quality and color, and some phones are now even incorporating SmartMedia cards to contain and transmit personal data, Katcher said.
"Often consumers are confused by a number of the technical terms that are applied in the description of a cell phone," said Kelly. "TDMA, FDMA, CDMA... they're all simply methods a phone will use for transmitting information, one method isn't really better or worse then another, they're just different ways of accomplishing the same task," said Kelly.
What people do need to understand are the capabilities of the systems they plan to use their phones on. They need to understand what PCS and GSM mean, they need to know the benefits of an all digital network, what dual/triple mode means, why they can't use certain phones internationally, and what they have to change to other phones to do the same, Kelly finished.
Personal Communications Services (PCS) is a wireless phone service that focuses more on data then phone technology. It is based more on paging, caller ID, email, pictures and video then anything else, it's like an add on service said Khan. "It's like an American version of GSM," he said.
Analog cellular systems in the United States operate in 824 MHz to 894MHz frequency bands while digital PCS operates in the 1850 MHz to 1990 MHz Bands.
Global System for Mobile Communications (GSM) is the international standard for cell-phone technology in Europe, Australia and the majority of Asia and Africa. In covered areas, cell phone users can buy one phone that will work anywhere where this standard is supported, Kelly said.
GSM was established in Europe in the 1980's, far before America realized it's capabilities with data streaming. GSM is a form that allows consumers phones to be located down to a few meters, the 3G (or third generation wireless) GSM phones incorporate PDA features such as video-conferencing, multi-player video gaming and advanced personal calendar functions.
GSM operates in the 900 MHz and 1800 MHz bands in Europe and Asia, and the 1900 MHz (sometimes referred to as 1.9 GHz) in the United States, said Holland.
To connect to specific service providers in different countries, GSM users only have to switch Subscriber Identification Module (SIM) cards. These cards are small removable disks that slip in and out of GSM cell phones. They Store all the connection data and identification numbers you need to access a particular wireless service provider.
Unfortunately, the 1900 MHz GSM phones used in the United States are not compatible with the international system.
"If a person needs cell phone access overseas, they have a few options, Cingular and Nextel are the only two service providers that have phones compatible with overseas networks; if a person has neither of those services, the easiest thing to do is to by a GSM 900MHz/1800MHz cell phone for traveling, but some providers also allow phone rental services for a few dollars a day," Katcher said.
"If you travel a lot, you will also want to look into duel and tri-mode phones," Kelly finished. A dual band phone has the capability to switch frequencies, allowing it to operate at both 800 MHz and 1900 MHz bands.
The term dual mode refers to the type of transmission technology used in the phone. This allows a phone to support two transmission standards such as AMPS -- for analog calling/roaming -- and TDMA -- for digital transmissions and data streams.
Most phones that are called tri-mode cover international GSM phones, meaning they support the 900 MHz band for Europe and Asia, and the 800 MHz (analog) and 1900 MHz (digital) bands for use in the U.S.
Most travelers should look into investing in a native tri-mode phones, where changing the SIM card will allow the users to use services all over the world.
Just a few of these phones are currently being produced by American providers, and each incorporates picture messaging, text messaging, phone book organization, and a host of other features that are beneficial to consumers on the go. SIM cards for most countries can be found on the internet, a popular place is www.telestial.com.
"Cell phone technology progresses so fast, it's hard to keep up, it's getting as bad as the computer industry in some cases," Katcher said.
"A brand new phone these days will be outdated in six months easy," said Khan.